Oxymethylene copolymers



3,072,609 OXYMETHYLENE COPOLYMERS Frank Berardinelli, South Orange, 'and Robert W.

Stevenson, Plainfield,'N.'J., assignors to Celanese' Corpora-tion' of America,"New York, N.Y., a corporation of Delaware No Drawing. Filed June 22, 1959, Ser. No. 821,719

" 14 Claims. (Cl. 260-67) This inventionrelates' to-novel'copolymers of high thermalstab'ility and'particularly to copolymers of trioxane.

Polyoxymethylene polymers, having recurring units have been known for inany years. They may be prepared'by thepolymerization of anhydrous formaldehyde or by the polymerization of trioxane which is a cyclic trimer of formaldehyde.

Trioxane may be polymerized to produce a moldable polymer of high thermal stability, particularlyin the preseuce of a boron fluoride-containing catalyst such as a boron fluoride coordinate with an organic compound in which oxygen or sulfur is the donor atom.

It has now been found that useful moldabl'e polymers comprising oxymethylene groupsand 2-chloromethyl oxyethylene groups oem-02F) CHzCl may be obtained by copolymerizing trioxane with epichlorohydrin or 4-chloromethyl-1,3-dioxolane.

The preferred catalysts used in the preparation of the desired copolymers are the boron fluoride coordinate complexes with organic compounds in which oxygen or sulfur is the donor atom and boron trifluoride ga's itself.

The coordinate complexes of boron fluoride may, for example, be a complex with an alcohol, a phenol, an acid, an ether, an acid anhydride, an ester, a ketone, an aldehyde, a dialkyl sulfide or a mercaptan. Boron fluoride etherate, the coordinate complex of boron fluoride with diethyl ether is the preferred coordinate complex. Boron fluoride dibutyl etherate is also highly desirable. The boron fluoride complexes which may be used include complexes with ethanol, with methanol, with propanol,

with butanol, with methyl acetate, with ethyl acetate, with phenyl acetate, with benzoic acid, with acetic anhydride,

with acetone, with methyl ethyl ketone, with dimethyl ether, with methylphenyl ether, with acetaldehyde, with chloral, with-dimethyl sulfide and with ethyl mercaptan. Coordinate complexes of boron fluoride with water, such as boron fluoride monohydrate, boron fluoride dihydrate and boron fluoride trihydrate may also be used. 1 The coordinate complex of boron fluoride should be present in the polymerization zone in an amount such that its boron fluoride content is between about 0.001 and about 1.0 weight percent based on the weight of trioxane and comonomer in the polymerization zone. Preferably, amounts between about 0.003 and about 0.1. weight percentshould be used. 7

While it is-not desired tobe bound by any-theory, it is believed that epichlorohydrin, under the polymerization conditions, opens its ring between a carbon atom and the oxygen. atom to produce a Z-chloromethyl oxyethylene group and that 4-chloromethyl-1,3dioxolane opens its ring between a carbon atom and an oxygen atom toIproduce a linear structure comprising an oxymethylene group linked to a 2-chloromethyl oxyethylene group.. The trioxane and comonomer in the reaction zone are preferably anhydrous or substantially anhydrous. Small amounts of moisture, such as may be presentin commercial grade feed materials or may be introduced, by

contact withatmospheric air will not prevent polymerization, but should be removed for best yields.

In oneembodiment of this invention the trioxane is polymerized in its molten state with the'comonomer and catalyst dissolved therein. The preferred temperature for such polymerization is between about 0 and about 100 C. The period of reaction for such polymerization may vary from about 2 minutes to about 72 hours. Pressures from subatmospheric to about 100 atmospheres, or more, may be used, although atmospheric pressure is preferred.

In another embodiment of this invention, the trioxane, comonomer andcatalyst are dissolved in a common anhydrous solvent, such as cyclohexane, and permitted to react. The temperature for solution polymerization of this type may vary from about 10 C; to about C. The period of reaction in such polymerization may vary from about /2 hour to about 72 hours. mers of exceptionally high molecular weight it is desirable to initiate the polymerization in solution and to then drop the temperature so that most of the trioxane precipitates and to complete the polymerization in solid phase. I In the polymers of this invention, the 2-chloromethyl oxyethylene groups will be present in weight proportions between about 0.1 and40 weightpercent based on the weight of total polymer. Since thechlorine-containing comonomer combines vigorously with itself, it may be desirable to add at least a portion of the comonomer after the polymerization has initiated in order to avoid depletion thereof before the completion of thepolymerization.

In producing the copolymers the weight ratio of the chlorine-containing comonomer to the trioxane may vary from about 2 to about 0.005 part of comonomer per part of trioxane in the reaction zone with the higher ratios being associated with delayed addition, as described above. Preferably, the weight ratio may vary from about 1 to about 0.01 part of comonomer per part of trioxane.

In addition to the oxymethylene and 2-chloromethyl oxyethylene groups, the polymer of this invention may comprise other recurring structural groups and particu larly oxyalkylene groups having at least two carbon atoms. Oxyethylene groups are particularly desirable and may be incorporatedinto the polymer structure by including in the reactant mixture the desired amount of a cyclic ether having two adjacent carbon atoms, such as ethylene oxide or dioxolane. A suitable range of proportions for incorporating such a cyclic ether in the reaction mixture is between about 1 and weight percent, based on the weight of trioxane, with higher proportions being associated with delayed addition. In the polymer, oxyethylene groups may suitably comprise between about 0.1 and 40 weight percent of the polymer. The combined weight of oxyethylene and -2-chloromethyl oxyethylene groups will generally not exceed 50% of the weight of the polymer. Upon completion of the polymerization reaction where arelatively large amount of catalyst has been used it is desirable to neutralize the activity of the catalyst since prolonged contact'with the catalyst degrades the polymer. The polymerization product may be treated with an aliphatic amine, such as tri-n-butylamine, in stoichiometric excess over the amount of free catalyst in the reaction product, and preferably in an organic wash liquid which is a solvent for unreacted trioxane. Or, if desired, the reaction product maybe Washedwith water which neutralizes catalyst activity. A detailed description of the methods of neutralizing catalyst activity may be found in copending application S. No. 718,147, filed February 28, 1958', by Donald E. Hudgin and Frank M. Berardinelli.

EXAMPLE I solution of 39.2 grams of trioxan-e, 168 grams of cyclohexane and 9.8 grams ofepichlorohydrin was heated Patented Jan. 8, 1953 To obtain poly- 3 at 60 C. and 0.12 ml. of boron fluoride dibutyletherate in 3.0 ml. of cyclohexane was added. The reaction mixture was maintained at 60-61 C. for 2% hours, after which it was cooled to 50 C. and 1 ml. of tributyl amine indicating a 2-chloromethyl oxyethylene content of about 2.3% in the terpolymer.

EXAMPLE XIV in 300 ml. of acetone was added. The polymer was fil- 5 tered off, washed three times with acetone and dried at To a three-necked flask q pp with stirrer and drop- 60-65 C. 260 grams f polymer r b i d, A ping funnel were charged 180 grams of trioxane, 100 ml. sample of the polymer, combined with 2 weight percent of cyclohexane, and the temperature brought to 56 C. of 2,2'-methylene bis (4-methyl-6-tertiary butyl phenol) There was added 0.029 ml. of boron trifluoride dibutyl as a stabilizer, was molded into a tough disc at 190 C. ethefate in 5 1111- Of cyclohexane, and at the Same time for four minutes. the addition of 20 grams of 4-chloromethyl-1,3-dioxolane was begun from the dropping funnel. The addition of EXAMPLES II To XII the comonomer at a uniform rate required 86 minutes,

A series of polymerization reactions were run in which during which time the flask temperature was maintained cyclohexane constituted 30 weight percent of the total at 5660 by means of external heating. The mixture charge. The trloxane and initial epichlorohydrin were was then kept at 50 overnight, after which time the d1ssolved 1n 91% of the cyclohexane and heated at 60 polymer was recovered. After stirring for 15 minutes C. for about /2 hour. The catalyst (boron fluoride dieach with five ml. of tributylamine in methanol, methanol, butyl etherate), dissolved in the remaining 9% of the and hot water (twice), the polymer was dried at 70. total cyclohexane was then added. Additional epichloro- The melting point of the polymer was 168173 C. hydrm was added (except in Example V) when the polym- Chlorine analysis indicated 1.13% chlorine by weight, erlz ation had progressed just beyond the point of inor about 2.9% of 2-cl1loromethyl oxyethylene units in cipient cloudiness of the reaction mixture. The period the polymer by weight. of add1t1on of the delayed epichlorohydrin was 90 min- It is to be understood that the'foregoing detailed deutes at a roughly uniform rate of addition, except in scription is given merely by way of illustration and that those examples where the total reaction time was shorter. many variations may be made therein without departing After completion of the reaction period, 50 ml. of from the spirit of our invention. 4 acetone was added to the mixture and stirred for a few Having described our invention what we desire to minutes. The material was filtered and subjected to three secure by Letters Patent is: cycles of slurrying in acetone and filtration. The poly- 1. A copolymer consisting essentially of recurring mer powder was dried overnight in a circulating air oven oxymethylene groups and recurring 2-chloromethyl at a temperature less than 100 C. oxyethylene groups.

The reaction proportions, reaction time and tempera- 2. A copolymer consisting essentially of recurring ture, and the melting point, chlorine content and oxyoxymethylene groups, recurring oxyethylene groups and: methylene content of the polymers are shown in the folrecurring 2-chloromethyl oxyethylene groups. lowing table: 3. A copolymer consisting essentially of recurring Table I g. Epichlorohydrin Reaction Wt. Reaction Percent Example g. Tri- Time Percent Temp. M. Pt. Percent oxymeth- No oxane (Hrs) Catalyst 0.) 0.) Cl ylenc Initial Delayed 160 5 31 3 0. 021 60-45 112-130 6. 57 82. 9 180 2 1s 1 0. 021 60-45 151165 2. 03. 6 90 2 8 ,4 0. 021 60-45 149-158 2. 62 93. 2 180 6 0. 021 165-173 0. s5 97. s 90 a 7 2 0. 01 60-45 120-147 4. 55 as. 1 180 3 6 114 0. 021 45 106-138 4. 66 87. 0 180 4 8.4 144 0. 01 45 164-176 0.82 97.8 180 2. 6 17. 4 1y. 0. 01 160179 0. 52 98. 6 180 2. 4 4 14 0. 01 45 167-185 0. 80 97. 9 180 2 17 2% 0. 007 50 153-173 1. 77 95. 4 180 19% 2141 0.005 52 123-153 5. 17 86. 5

I Temperature rose by exothermic heat of reaction to a maximum of 99 C;

EXAMPLE XIII To a three-necked 500 ml. flask equipped with a stirrer and dropping funnel were charged 180 grams trioxane, 5 grams dioxolane, and 80 grams of cyclohexane. Provision was made so that 15 grams of 4-chloromethyl-l,3- dioxolane could later be introduced to the reaction mixture from a dropping funnel. The flask charge was brought to C. and 0.05 ml. of boron trifiuoridedibutyl etherate in 8 grams of cyclohexane was added. After a half-hour induction period, the flask was heated to 59 and the polymerization had begun. The addition of the comonomer, 4-chloromethyl-1,3-dioxolane, was be. gun at this time and continued over a 35 minute period. Additional catalyst, 0.06 ml. boron trifiuoride in 8 ml. cyclohexane was added at this time. The reaction was self-sustaining at -65 for the next half hour. After standing overnight, the polymer was washed successively with tributylamine in methanol, methanol, and hot water. The melting range of the polymer was 164l69 C. and the IV. as measured in 0.1% solution in 98 parts pchlorophenol and 2 parts a-pinene was 0.74. The polymer analysis gave a value of 0.88% chlorine by weight oxymethylene groups and 0.1 to 40 weight percent of recurring 2-chloromethyl oxyethylene groups.

4. A copolymer consisting essentially of recurring oxymethylene groups, 0.1 to 40 weight percent of recurring 2-chloromethyl oxyethylene groups and 0.1 to 40 weight percent of recurring oxyethylene groups with the combined weight of 2-chloromethyl oxyethylene groups and oxyethylene groups not exceeding 50 weight percent of the polymer.

5. A method of preparing a moldable copolymer which comprises copolymerizing trioxane and from 0.01 to 1 part by weight of a comonomer of the group consisting of epichlorohydrin and 4-chloromethyl-1,3-dioxo1ane per part of trioxane.

6. A method of preparing a moldable copolymer which comprises copolymerizing trioxane and from 0.01 to 1 part by weight of epichlorohydrin per part of trioxane.

7. The method of claim 5 wherein said polymerization is carried out in the presence of a catalyst comprising a boron fluoride complex with an organic compound in which oxygen is the donor atom.

8. The method of claim 5 wherein said polymerization 5 is carried out in the presence of a catalyst comprising gaseous boron fluoride.

9. The method of claim 5 wherein at least a portion of the epichlorohydrin is added to the reaction zone after polymerization has been initiated.

10. A method of preparing a moldable copolymer which comprises copolymerizing trioxane, between 1 and 100 weight percent of a comonomer of the group consisting of epichlorohydrin and 4-chloromethyl-1,3-dioxolane and between 1 and 100 Weight percent of a second comonomer of the group consisting of ethylene oxide and dioxolane, both percentage ranges based on the weight of trioxane.

11. A method of preparing a moldable copolymer which comprises copolymerizing trioxane and from 0.01 to 1 part by weight of a comonomer of the group consisting of epichlorohydrin and 4-chloromethyl-1,3-dioxolane per part of trioxane at a temperature between 0 and 100 C. in the presence of a catalyst of the group consisting of gaseous boron fluoride, boron fluoride co- 20 ordinate complexes with water, and boron fluoride coordinate complexes with organic compounds in which the donor atom is selected from the group consisting of oxygen and sulfur.

12. The method of claim 11 wherein said polymerization is carried out at a temperature between about 0 and 100 C. in the presence of a catalyst of the group consisting of gaseous boron fluoride, boron fluoride coordinate complexes with water, and boron fluoride coordinate complexes with organic compounds in which the donor atom is selected from the group consisting of oxygen and sulfur.

13. A copolymer of trioxane and a comonomer of the group consisting of epichlorohydrin and 4-chloromethyl- 1,3-dioxolane.

14. A copolymer of trioxane, a comonomer of the group consisting of epichlorohydrin and 4-chloromethyl- 1,3-dioxolane and a second comonomer of the group consisting of ethylene oxide and dioxolane.

References Cited in the file of this patent UNITED STATES PATENTS 2,395,265 Gresham Feb. 1, 1946 2,625,569 Gresham Jan. 13, 1953 FOREIGN PATENTS 486,015 Great Britain May 27, 1938 

13. A COPOLYMER OF TRIOXANE AND A COMONOMER OF THE GROUP CONSISTING OF EPICHLOROHYDRIN AND 4-CHLOROMETHYL1,3-DIOXOLANE. 